Method of synthetizing tertiary aliphatic amines by amination of alkyl halides

ABSTRACT

This invention is directed to the production, by synthesis, of tertiary aliphatic amines by amination of alkyl haloids, by means of secondary aliphatic amine, wherein a reaction mixture is prepared which consists of two fractions, one fraction comprising at least one alkyl haloid consisting mainly of halogen-1-alkane, the other fraction consisting of a secondary aliphatic amine within an aprotic dipolar solvent capable of dissolving the halide and the secondary amine but not of appreciably dissolving in the cold state the resulting tertiary aliphatic amine, whereby operation at relatively low temperatures and pressure values can be performed.

United States Patent" [191 Pivette Oct. 9, 1973 [30] Foreign Application Priority Data Dec. 23, 1969 France 6944604 Dec. 9, 1970 France 7044332 [52] U.S. Cl. 260/583 R, 260/585 A 51 Int. Cl. C07c 85/04 [58] Field of Search 260/583 R, 585 A [56] References Cited UNITED STATES PATENTS 3,471,561 10/1969 Dadekian et a1 260/583 R 3,542,876 11/1970 Blaney 260/583 R METHOD OF SYNTHETIZING TERTIARY ALIPHATIC AMINES BY AMINATION OF ALKYL HALIDES Appl. No.: 99,853

3,491,151 1/1970 Bader 260/584 R Primary Examiner-Lewis Gotts Assistant Examiner-Richard L. Raymond Attorney-Stevens, Davis, Miller & Mosher [57] ABSTRACT This invention is directed to the production, by synthesis, of tertiary aliphatic amines by amination of alkyl haloids, by means of secondary aliphatic amine, wherein a reaction mixture is prepared which consists of two fractions, one fraction comprising at least one alkyl haloid consisting mainly of halogen-l-alkane, the

other fraction consisting of a secondary aliphatic amine within an aprotic dipolar solvent capable of dissolving the halide and the secondary amine but not of appreciably dissolving in the cold state the resulting tertiary aliphatic amine, whereby operation at relatively low temperatures and pressure values can be performed.

11 Claims, 1 Drawing Figure ,W LlPEE L iEWlUE-a METHOD OF SYNTHETIZING TERTIARY ALIPHATIC AMINES BY AMINATION OF ALKYL HALIDES The present invention relates to the production by synthesis of tertiary aliphatic amines by amination of alkyl halides.

The following methods of synthetizing tertiary amines are already known:

a. Action of formol and formic acid on a fatty primary amine (Eschweiler Clarkes reaction). In this process, hydrogen may be substituted for formic acid.

Apparently, this reaction has a complicated mechanism and the maximum observed yield is about 80 percent.

b. Action of formol and hydrogen on fatty nitrile.

This reaction starts at a preparation step antecedent to the one resulting from the above-mentioned process (a), in that the initial material is nitrile in lieu of amine. The yield is of the same order of magnitude as that of method (a).

0. Action of dimethylamine on a fatty alcohol.

This reaction takes place under a relatively high pressure of the order of 200 to 300 bars (2,900 to 4,350 psi).

d. Action of a dialkylamine and notably dimethylamine on an alkyl halide.

This reaction has also been known for a long time and may be written in the form:

RI RX+HN K. wherein R designates an alkyl, X a halide, R and R" low-molecular weight alkyl radicals such as methyl, ethyl, propyl, etc.

As a rule, this reaction takes place in an aqueous medium at temperatures within the range of 50 to 190 C. The pressure normally reached during the reaction is generally of the order of 40 to 50 bars (580 to 725 psi) and may sometimes exceed 80 bars (1,160 psi). This reaction is complete and rapid only if a considerable excess of dialkylamine of the order of 12 to 18 moles per mole of alkyl haloid is used.

If the dialkylamine molar excess is only of the order of 2 to 3 moles per moles of halide, the reaction time requires generally more than 3 hours, thus impairing the economy of the process and the final quality of the resulting tertiary aliphatic amine.

From this last-named process, the present invention aims at avoiding the inconveniences set forth hereinabove which reside chiefly in the use of relatively high temperatures and pressures during a considerable time period.

With the method of this invention for the production of tertiary aliphatic amines by amination of an alkyl halide by using a secondary aliphatic amine is characterized in that a reaction mixture is prepared which comprises two fractions, the first fraction consisting of at least one alkyl haloid and comprising a major part of halogen-l-alkane, the other fraction consisting of a secondary aliphatic amine within an aprotic dipolar solvent capable of dissolving both the halide and the secondary amine but not capable of appreciably dissolving, in the cold state, the resulting tertiary In fact, it was observed that aprotic dipolar solvents are capable of dissolving at the same time considerable amounts of alkyl halides and secondary amines as used for the synthesis of tertiary amines, without appreciably dissolving these last-named amines in the cold state. Therefore, the reaction takes place in a homogeneous medium, in contrast with most of the other processes mentioned hereinabove.

It has been found that as a result of the practical application of this method the use of this type of solvent will increase considerably the amination reaction rate and therefore permit of operating at considerably lower temperature and pressure values than in said prior art methods.

Moreover, as it is not soluble in the medium the tertiary amine resulting from the reaction can be extracted or recovered by using a simple physical step consisting, for example, of a decantation which can then be followed by a distillation.

According to this invention, the halide is halogenalkane obtained by hydro-halogenation of alphaolefmes, according to a radical or so-called abnormal reaction. It comprises as a rule four to 22 carbon atoms and preferably eight to 18 carbon atoms. Also preferably, bromo-alkanes consisting of a major part of bromo-l-alkane will be selected. However, bromides may be replaced by chlorides. Nevertheless, it should be born in mind that it is much more difficult to obtain chloro-l-alkane of adequate grade from starting mate rials of petroleum origin.

Said first fraction of the reaction mixture advantageously contains at least 85 percent by weight of halo- I gen-l-alkane.

f The secondary amines used in the process of this invention correspond to the general formula:

NH I wherein R and R" are safirated or unsaturated alkyl radicals containing one to 18 carbon atoms and preferably one to four carbon atoms.

These secondary amines are symmetric or asymmetric. They consist preferably of dimethylamine, diethylamine, diallylamine, dipropylamine and diethanol amine.

A molar ratio of 2 moles of secondary dialkylamine per mole of alkyl bromide (or chloride) is used, this excess being sufficient for fixing the hydrobromic (or hydrochloric) acid released during the reaction:

' R R R solvent The crude tertiary amine thus obtained is free of alkyl halide and its degree of purity is generally in excess of 90 percent by weight; the product is colourless and a simple removal of the first fraction of the product by distillation yields an amine having a degree of purity in excess of 98 percent.

It may also be noted that no quaternary ammonium is released or formed during the reaction.

Finally, the reaction is carried out under a pressure above the atmospheric value but below 4 bars (58 psi).

Various modes of embodying the method of this invention are described hereinafter by way of example. In these examples the fractions, portions and percentages are given by weight.

Example 1 In a reactor capable of withstanding a pressure of about 2 bars (30 psi) a solution of 360 parts of dimethylamine in 1,200 parts of dimethylformamide is reacted with 1,100 parts of bromo-l-tetradecane prepared by hydrobromidizing tetradecene-l. Within minutes the temperature rises spontaneously to 80 C. Then the temperature is raised to 150 C during 45 minutes, the pressure remaining equal or inferior to 1 bar (14.5 psi) during this period, and then the reagents are allowed to cool to room temperature. The reaction mixture separates spontaneously into two layers. After removal of the lower or bottom layer, 993 parts of a clear, colourless product are collected which contain 90.2 by weight N-dimethyltetradecylamine, 9 b.w. hydrocarbons and 0.5. by weight dimethylamine. This product is free of unreacted bromoalkane, quaternary ammonium salts and hydrobromic acid, and can be purified very easily by simply removing the head under reduced pressure, thus yielding N-dimethyltetradecylamine having a degree of purity in excess of 98 by weight. Example 2 In a process similar to that described in example 1, hexamethylphosphorotriamide was substituted for dimethylformamide in the same proportions. From the same amounts of dimethylamine and tetradecyl bromide, and after removing the bottom layer, 990 parts of crude amine containing 89.7 by weight N-dimethyltetradecylamine, 0.6 dimethylamine and 9.1 by weight hydrocarbon were collected. Example 3 In a reactor capable of withstanding a pressure of about 2 bars psi) a mixture consisting of 1,100 parts of tetradecyl bromide containing 95 by weight bromo-l-tetradecane and 1,180 parts of a 32 b.w. dimethylamine solution in N-methylpyrrolidone is stirred. The temperature rises spontaneously to 80 C, the pressure within the reactor rising likewise to about 0.5 bar (7.25 psi); the stirring is discontinued and the mix allowed to cool to room temperature; then, after removing the bottom layer separating spontaneously by decantation, a clear, colourless product containing 76.6 by weight of N-dimethyltetradecylamine, 1 b.w. of dimethylamine, 8.l by weight of hydrocarbons and 6.1 b.w. of tetradecyl bromide is obtained. Example 4 In a process similar to the one described in Example 1 and by utilizing n-decyl bromide and dimethylamine dissolved in dimethylformamide, the reagents being used in the same molar proportions as inExample l, a clear, colourless product was separated by decantation and after removal of the head under reduced pressure this product gave substantially pure N- dimethyldecylamine with a 86 yield with respect to alkyl bromide. Example 5 In a flask equipped with an agitator 97 g (1 mole) of diallylamine, 100 g of dimethylformamide and 138.5 g (0.5 mole) of tetradecyl bromide are introduced. The mix is heated during 2 hours, while stirring, to C; the previously homogeneous reaction mixture thus separates into two fractions. These fractions are allowed to cool to room temperature and the stirring is discontinued. The upper layer consisting mostly of N-diallyltetradecylamine was subjected to a fractional distillation under reduced pressure and yielded a high percentage of N-diallyltetradecylamine having a high degree of purity.

In the preceding examples the alkyl haloid utilized was bromide. Advantageous results may also be obtained from chlorides as shown by the following example 6.

Example 6 in a reactor capable of withstanding a pressure of about 2 bars (30 psi) a mixture consisting on the one hand of 1,100 parts of a dodecyl chloride containing 93 by weight of chloro-l-dodecane manufactured by chlorinating dodecyl alcohol, and on the other hand of 1,120 parts of a 40 solution of dimethylamine in dimethylformamide was stirred. The temperature increased to 150 C, so that the pressure in the reactor attained 0.7 bars (11.15 psi). The stirring was discontinued and the liquid is allowed to cool to room temperature.

After decantation and removal of the bottom layer, a clear, colourless product was obtained which, after removing the head, yielded N-dimethyldodecylamine having a degree of purity in excess of 98 by weight, with a yield of 88 in comparison with alkyl chloride.

The method and its various forms of embodiment disclosed hereinabove are adequate for a batchwise production of tertiary amines. Now, it was also attempted to take advantage of the relatively easy separation of the reaction product for performing a continuous reaction process.

However, it was found that as the reaction proceeds the increment in the secondary amine halohydrate is attended by a substantial reduction in the quantity of unreacted alkyl haloid and of the resultant tertiary amine, so that these two compounds have a natural tendency to become jointly separated from the reaction medium, the halide becoming soluble in the tertiary amine. As a result, a strong agitation is necessary for completing the reaction, the latter taking place in a heterogenous phase and leading to an undesirable percentage of quaternary ammonium halide.

Now it was discovered that this inconvenience could be removed by compensating the reduction in solubility of alkyl halide and tertiary amine by gradually increasing the temperature during the reaction.

On the other hand, it was also found that the quantity of solvent utilized must be such that all the products and subproducts of the reaction remain in solution throughout the reaction time; as a result, the product obtained by cooling and decantation consists nearly wholly of the formed aliphatic tertiary amine. This result is obtained when the ratio, by weight, of solvent utilized to the alkyl halide input ranges from 2:1 to 5: l.

This invention is also applicable to a method permitting of producing tertiary amine as a continuous prosurface-type heat exchanger through which a suitable cooling fluid is circulated, and opens into a decanter 9.

This decanter 9 consists of a closed vessel provided at its upper portion with a pipe 10 for exhausting the F h t f being characterized in h t 5 excess dimethylamine in the gaseous state, a lateral tion mixture circulated and exposed during 1ts clrcu- Outlet pipe 11 leading from the upper portion of the 13mm t a gradually mcreasmg telnperamre and that canter for recovering the crude tertiary amine formed the ratio of solvent to the alkyl halide ranges from 2:1 in the liquid State, and, at the bottom another pipe 12 to 5:1 by welght the macho Product h Subse' bent to an S shape (turned about 90in its plane) for q h y then decanted cohtmuously P 10 discharging the bottom solution of dimethylamine hyeratlhg decahtmg Vesseldrobromide in dimethylformamide. A small vertical Thus, e reduction ht the solublhty of thet'ol'med tube 13 opening into the atmosphere extends from an tertiary amme and of the unreacted alkyl halide as a upper point f this pipe 12 to prevent the latter from function of the increment in the secondary amine acting as a Siphon 15 ialohydrate 1S q i i as the mac The conventional accessorles mherent to chem1cal t1on proceeds by the increase 1n solubility due to the apparatus of this character, such as supports, brackets, gradual temperature increment and, on the other hand,

pumps, metering devices valves and sundry brassthe vapour pressure increment of the secondary amme, f

. ounding art1cles, as well as measurmg and regulatmg as a consequence of the reduct1on 1n the solubility of 1nstrumer1ts, are not shown as then type, posmon and this amine when the temperature increases, 1s compen- I arrangement will read1ly occur to those conversant sated by the amine consumption as the reactlon prowith the an ceeds, due to the very temperature increment.

Under the thus established reaction conditions, the 9? mplememmg the above'descnbecl apparatus crude tertiary amine separating spontaneously from the g t elements 3 are ope'rated for f the column reaction mixture is free of alkyl haloid, quaternary amwlth temperature grad'em compnsl'gg regular Steps monium salt and secondary amine halohydrate. Moremcreasmg from bottom to top from 20 to 150 over, its coloration is inferior to l Gardner (according The alkyl bromide and secondary amine in solution to the US Standard ASTM D255, Gard r C l Stanin the solvent are introduced into the bottom portion dards, 1953). of column 2 via conduits 4, 5 and 6, the outputs being Moreover, the pressure may be kept at a value below adjusted by means of suitable metering pumps (not 2 bars (about 30 psi) so that the necessary apparatus Shown). The reaction mixture is taken from the top of is simplified with the additional advantageous feature the C lumn and directed through the cooler 8 to the that the process may be carried out in a suitable glass continuously operating decanter 9 where the amine is or plastic apparatus, so that pollutions by metal salts r vered in th upper phase with a degree of purity can safely be avoided. approximating the impurities being ascribable By way of example, the continuous manufacturing chlefly to the 1n1t1almater1als. method of this invention may be Carried ut in an ppa- The rate of feed of the raw materials corresponds to ratus of the type illustrated diagrammatically in the sina e ti n ti of 4 t 15 mi ute gle FIGURE of the attafmed drawmg' 40 The molar ratios of secondary amine to alkyl halide This apparatus comprrses a reactor 1 conslstmg ofha are within the range of 2:1 to vemcal colufmn g zfl i t??? a hlelg t The'amounts of solvent utilized are by weight in the a f T proportion of 211 to 5:1 by weight of the alkyl halide 2 1s prov1ded w1th a plurahty of heating elements 3 such input as coil tubes or the like disposed at spaced intervals 5 Ali] h th d t b d along the longitudinal axis of the column and supplied h t oug e i amlne exces 0 t 1 with heating fluid at different temperatures so that the l lg i re atwe y reacuon fa e 18 re temperature within the reaction column 2 increases uve y lg from bottom to top. Advantageously, the column 2 y emerge from the eohdults 12 and the comains fining bodies (not shown) Such as R hi actlon by-products as well as the solvent are recovered rings. This column 2 is fed from the bottom whereby and e ye y ll h e Suitable means alkyl bromide is supplied through a conduit 4, dimethnot wlthlh the Scope of the lhvehtlohylformamide through another conduit 5 and dimethyl- The following table gives the numerical data conamine through a branch conduit 6 leading into conduit cerning eight tests of continuous tertiary amine produc- 5, as shown, tion according to the method of this invention, the sol- A complementary conduit 7 leads from the top of vent consisting in all cases of dimethylformamide, and column 2 down into a cooling device 8 consisting of the secondary amine consisting of dimethylamine.

. TABLE Dimethyl- DimethyI- i oercemcliiposmon of No. of amine to formamide crude tert. amine alkyl Alkyl alkyl to alkyl Crude radical Bromobromide bromide bromide amine Quatem.

Test carbon l-alkane output molar molar Temp. output Alkyl ammonium Yield No. atoms b.w.) (kg/hr) ratio ratio (Cl (kg/hr) Amine brom. salts (76) 3 14 91.2 15 2.1/1 2.2/1 20 3 13.1 88.2 traces 6 94 TABLE Conlinued Dimethyl- Dimelhyl- Percent composition of No. of amine to formamide crude ten. amine alkyl Alkyl alkyl to alkyl Crude radical Bromobromide bromide bromide amine Quatern. Test carbon l-alkane output molar molar Temp output Alkyl ammonium Yield No. atoms (Z1 b.w.) (kg/hr) ratio ratio (C) (kg/hr) Amine brom. salts (72) 5 14 92.6 15 2.3ll 3.251! 2011 13.05 86.3 1.4 0 H 120 6 ill 88 3.2/1 3/l 20a 8.65 87.6 0 0 94.8

140 7 IO 94.4 2.9!] 3/1 I16 88.] 0 0 94.2

140 8 I2 93, 4 l5 3/] 3/l 20 a0 13 88.0 0 O 95.]

The yield mentioned in this table was calculated as follows:

P X 100/p wherein P denotes the total weight of pure tertiary amine contained in the resultant crude amine, and p the weight of amine to be theoretically obtained from the bromo -l-alkane contained in the crude alkyl bromide utilized. i

What is claimed as new is:

l. A process for the continuous production of aliphatic tertiary amines comprising circulating together in a reactor at least one alkyl hads s tin ssenti ly ha -7 1 9: les

one aliphatic secondary amine and at least one anhydrous organic solvent adapted to dissolve the raw materials and the byproducts of the reaction and not appreciably dissolve in the cold state the resulting aliphatic tertiary amine, said solvent being selected from the group of dipolar aprotic solvents comprising dimethyl formamide, hexamethyl phosphorotriamide, tetrahydrofuran and N-rnethylpyrrolidone,

heating the mixture of said materials to a temperature of about 150 C,

passing said mixture through a cooler and into a separator in which the resulting liquid separates into two layers, and

' collecting from the top layer the liquid aliphatic tertiary amine which has been produced.

2. A process according to claim 1, wherein said alkyl halideis a halo-l -alkane produced by hydrohalogenation of olefins according to a radical reaction.

3. A process according to claim 1, wherein the alkyl halide contains at least by weight of halol-alkane.

portion of secondary amine and alkyl halide is such that there is a molar ratio of at least two molecules of secondary amine to one molecule of alkyl halide.

8. A process according to claim 1, wherein the secondary amine is introduced into the reactor after having been mixed with the solvent.

9. A process according to claim 1, wherein the mixture is heated to a temperature which increases as the mixture flows through the reactor.

10. A process according to claim 1, wherein the reaction is carried out at a pressure higher than atmospheric pressure and less than 4 bars.

11'. A process according to claim 1, wherein the reaction mixture is kept at a pressure below 2 bars while it is subjected to a progressively increasing temperature. 

2. A process according to claim 1, wherein said alkyl halide is a halo-1-alkane produced by hydrohalogenation of olefins according to a radical reaction.
 3. A process according to claim 1, wherein the alkyl halide contains at least 85% by weight of halo-1-alkane.
 4. A process according to claim 1, wherein said alkyl halide is selected from the group consisting of the alkyl bromides and chlorides containing eight-22 atoms of carbon.
 5. A process according to claim 1, wherein each of the alkyl radicals of the secondary amine contains one-18 atoms of carbon.
 6. A process according to claim 1, wherein the quantity of solvent in relation to the alkyl halide is in the proportion of 2/1 to 5/1 by weight.
 7. A process according to claim 1, wherein the proportion of secondary amine and alkyl halide is such that there is a molar ratio of at least two molecules of secondary amine to one molecule of alkyl halide.
 8. A process according to claim 1, wherein the secondary amine is introduced into the reactor after having been mixed with the solvent.
 9. A process according to claim 1, wherein the mixture is heated to a temperature which increases as the mixture flows through the reactor.
 10. A process according to claim 1, wherein the reaction is carried out at a pressure higher than atmospheric pressure and less than 4 bars.
 11. A process according to claim 1, wherein the reaction mixture is kept at a pressure below 2 bars while it is subjected to a progressively increasing temperature. 